The purpose of this protocol is to determine the phase II response rate of melanoma and renal cell cancer to therapy with Topotecan, a topoisomerase I inhibitor and to determine whether GM-CSF given before chemotherapy prevents myelosuppression. All pts. receive Topotecan 1.5 mg/m2 daily by bolus IV infusion for 5 days and post-therapy GM-CSF 250 microgram/m2 daily. Pts. are randomized to receive no additional therapy or GM-CSF 250 microgram/m2 twice daily before Topotecan. 53 pts. have been entered on study, 28 pts. with melanoma and 25 with renal cell cancer. 51 pts. are evaluable for response, 27 with melanoma and 24 with renal cell cancer. One pt. with renal cell cancer had complete regression of his lung metastases but no response in his kidney primary. One pt. with melanoma had a partial response of his subcutaneous disease that lasted for 6 months prior to developing brain metastasis. No other responses were seen. A decrease in grade IV neutropenia following both the first and second cycle of Topotecan has been seen in pts. randomized to prechemotherapy GM-CSF. No protective or adverse effect on platelet counts was seen in pts. treated with GM-CSF before chemotherapy.